Regenerative braking system



Jan. 14, 1936. HERMLE 2,027,865

REGENERATIVE BRAKING SYSTEM Filed March 1, 1935 Inventor: Hermann Hermle,

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Patented Jan. 14,- 1936 UNITED STATES 2,027,865 BEGENERATIVE BRAKING SYSTEM Hermann Hermie, Berlin-Lankwitz, Germany, assignor to General Electric Company, a corporation of New York Application March 1,

1935, Serial No. 8,861

In Germany April 18, 1934 Claims. (01. 172179) My invention relates to regenerative braking systems of the general character shown by Letters Patent No. 1,976,562, Janisch, dated October 9, 1934, and has for an object the provision oi! a 5 simple and reliable means for preventing the flow of current of large magnitude which may be caused by an undue rise of the motor voltage. During regenerative operation of the traction motors of a vehicle the trolley or supply circuit may become deenergized or open circuited. For example, the supply circuit may be deenergized by the opening of a circuit breaker connected in the supply circuit, or the trolley may be moved onto a dead section of the supply line. Under such conditions the voltage oi the traction motors, operating as generators, rises considerably.

The rise in voltage is due in part to the speeding up of the vehicle and in part to an increase in the field excitation of the motors. Consequently; I

as soon as the trolley moves onto a live section of the supply circuit, or as soon as the supply circuit is again energized, the resultant current flow of large magnitude may cause damage to the motors.

In accordance with my invention in one form thereof, I provide a normally conductive valve betweenthe supply circuit and the regenerative brakingcircuit, and operate in response to the motor voltage a control device to render the valve non-conductive whenever the motor voltage rises above a predetermined value. The control device also operates to render. the valve conductive after the voltage or the motors has decreased below the predetermined value.

For a more complete understanding of my invention, reference should now be had to the accompanying drawing wherein I have shown diagrammatically a regenerative braking circuit embodying my invention. 7

ReierringtothedrawingJhaveshownmyinvention in one form as applied to a pair of trac-' tion motors II and I I provided, respectively, with field windings l2 and I3, resistors and L5 be- 5 1113 included in the field circuit. The regenerative'braking current fiows trom the motors l0 and II through a suitable electric valve l8 provided with an anode 11, a grid or control electrode I8, and a cathode I8. and by a trolley' 20 50 w supply line II, the motor current returning to the other side of the motors through the ground connection 22. The valve I i, preferably of the type having an ionizable gaseous medium within its enclosing 55 envelope. is capable of carrying currents of substantial magnitude. Valves of this type are well known to those skilled in the art.

Continuing with the description, it will now be assumed that the motors i0 and H are operating as generators to return current through the valve [6 to the supply circuit 2! and that the supply circuit is suddenly open circuited. Obviously, the flow of current from the regenerative circuit to the supply circuit is interrupted and the braking efiort exerted by the motors I0 10 and II substantially disappears. The voltage of the motors I0 and II immediately begins to rise, this rise in voltage in part being caused by a loss of the IR drop or voltage drop in the motors themselves. The rise in voltage is fur- 15 ther due to the increased speed of the vehicle caused by the loss of the braking effort. The total rise in voltage is of suflicient magnitude to produce a large flow 01' current, a current great enough to damage the motors, as soon as the 20 supply circuit is again closed.

'Inorder to prevent the flow of large magnitudes of current, I provide a source of supply such as a battery 23 arranged to be connected by a relay 24 for applying a negative bias to the 25 control electrode or grid It. The operating winding of the relay 24 is connected across the armature terminals of the motor ill and is arrangedto operate the relay contacts to closed position whenever the voltage of the motor In 30 rises above a predetermined value. As long as the voltage is above this predetermined value, the negative bias applied by the source 23 to the grid I8 renders the valve l6 non-conductive to current flowing in either direction. Consequent- 35 1y, when the supply circuit'fl is completed no current can flow from the motors I0 and H until the motor voltage decreases below the predeter- I mined value. Normally, the relay 24 is arranged to operate when the motor voltage exceeds by a 40 substantial amount the voltage of the supply circuit.

While I have shown a particular embodiment of my invention, it will be understood, of course, that 1 do not wish'to be limited'thereto since many modifications may be made, and I, therefore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What. I claim as new and desire to secure by Letters Patent of the United States, is:-

1. The combination with a regenerative braking. circuit for a motor arranged to return power to a supply circuit, 0! an electric valve connected between said circuits and normally conductive to current flowing from said regenerative circuit to said supply circuit; and means responsive to a predetermined voltage of said motor for rendering said valve non-conductive.

2. The combination with a regenerative'braking circuit for a motor arranged to return power. to a. supply circuit, of an electric valve connected between said circuits and'normally conductive only to current flowing from said regenerative circuit to said supply circuit, and means opera- 3. The combination with a regenerative braking circuit for a motor arranged to return' power to a supply circuit, of an electric valve ccnn'ecm between said circuits "and normally conductive to current flowing from said regenerative circuit a to said supply circuit, said valve normally prcventing the flow of power from said supplv tir-- cuit to said regenerative circuit irrespective of the voltage of said motor. and means operabl whenever the voltage of said motor exceeds the voltage of said supply circuit by a prmetermined amount for rendering said valve non-conductive.

i. The combination with a regenerative braking circuit for a motor arranged to return power to a supply circuit, of an electric valve pro-'- vided with ancnodc. a cathode and a control. electrode, means connecting said valve between -.sa.id supp y circuit and said motor. said valve a co 'v' acc normally being conductive for the flow of current from said motor to said'supply circuit and non-conductive for the flow of current from said supply circuit to said motor, and means responsive to a predetermined rise in the voltage of said motor -for applying a bias to said control electrode to rendersaid valve non-conductive to the flow 'of current from said motor to said supply circuit.

' 5. The combinationwith a regenerative brakto a'supply-circuit, of an electric valve provided with an anode, a cathode and a control electrode, means connecting said cathode to said supply circuit and said anode to said regenerative braking circuit, said valve normally being conductive to the flow of current from said mg circuit for a motor arranged to return power regenerative circuit to said supply circuit and 4 Qn-ctmductive to the fiow of current from. said supply circuit to said regenerative circuit, a relay provided with an operating minding, means connecting said in paiailel with the armature 'of said motor, said relay being operable in response to a predetermined voltage of 4 min m mm. 

